I have some serious doubts certaining the possibility of Tardust joining the good guys. Is he really indispensable? No, the "tech tree" he provides would be a nice addition though. At the moment however, he is not irrepalacable. What shall he actually do? Mixing chemicals? Running Analyses? I believe that this would not yield a great benefit because the overall zombieverse situation can be compared to the Coke recipe: you might know 98% of all ingredients it takes to create it but the rest of the yada-yada magic is hidden in Ink's brain. Another aspect: do you really want to have Tardust standing beside or behind you if you run into a confrontation with Scratch. Tardust cannot be called the pride of creation if it comes to mental stability...